Aqueous latex coating compositions, both clear and pigmented, are in wide use, the latex particles being provided by aqueous emulsion copolymerization of monoethylenically unsaturated monomers. These are generally thermoplastic from the standpoint that the deposited and air dried coatings dissolve easily in organic solvents, such as methyl ethyl ketone. When monomers providing cure capacity are present, the cure frequently requires a bake, and this largely limits curable coatings to industrial situations where baking capacity is available. When polyethylenically unsaturated monomers are included in the monomer mixture in the hope of obtaining residual unsaturation for subsequent cure after application, it is difficult to avoid premature consumption of all the unsaturation which impairs the capacity of the latex particles to coalesce and adhere to the coated substrate. In any event, utilization of the residual unsaturation to improve properties raises its own difficulties.
It is also known to employ driers to air cure unsaturated resins, but this is done in organic solvent solution, not in aqueous emulsion.
In my prior application Ser. No. 901,856 now abandoned, I provided an air drying latex coating composition containing unsaturated groups on the latex particles, but these were used to provide an ultraviolet light cure, particularly in the presence of appropriate photosensitizers. However, pigmentation of ultraviolet light-curing systems is difficult because most pigments are opaque to such light.